Generally, in an apparatus of the aforementioned type, a vacuum is initially created and then, the workpieces are heated by high energy ion-bombardment of cathode material vaporized by ARC discharge, and then the workpieces are coated by cathode material to the desired thickness of the coating film. The initial layer deposition is very important.
The ion bombardment of the prior technology has many essential problems for films coated by the vacuum ARC discharge.
It is known to coat workpieces, such as cast parts, tools, clock and watch cases, jewelry and the like, by a Ti-cathode in a vacuum. Ti-ions and droplets are evaporated from the Ti-cathode and are accelerated by a high bias potential of approximately DC 1000 V. At the workpiece, the ions release their thermal energy to the workpiece and heat the surface of the workpiece. The mechanism heats the substrate. However, the ions and droplets can migrate and adhere weakly to the surface.
Initially, relatively large particles, such as droplets reach the cold surface, and can be deposited on the surface. It has been found that if, during the further heating up of the surface and during the coating, ions are deposited alongside these particles, some particles can move below the initially deposited particles and force them upwards, so that an empty space forms beneath the same, which impedes coating. This process also initially leads to coarse coating with a limited density and wedge-shaped deposits, accompanied by a rough, uneven surface. Although in the case of further heating, a dense coating may be deposited on the first coating, it reduces the unevenness of the first deposits, quite apart from the fact that, because of the superimposed coatings of different structure, the necessary coating hardness is not achieved and instead easy peeling is possible due to the lower coating.